1. Field of the Invention
This invention relates to techniques for shifting subscriber information in a private exchange, and more specifically, to processes and circuits for maintaining subscribers' telephone numbers and grades or classes previously used even when any subscriber's telephone changes through alterations in the arrangement or line in a central office.
2. Description of the Related Art
A key telephone system or private exchange includes different subscriber numbers and grades or classes, so that different people can use one telephone number together. The grade or class refers to whether a subscriber is given the authority to just call others in the same office or to make local calls or to make long distance calls, or to modify the programming of the telephone system, etc. Such key telephone and private exchange systems are generally used in offices. Due to changes in the arrangement and lines in the office, the location of a telephone having a subscriber number and class may be changed. When the location of the telephone is changed, a new subscriber number and class must be provided. This involves a problem in that much time and expense are required.
Early efforts in the art, represented by the Method And Apparatus For Addressee Location patent issued to Kondo, U.S. Pat. No. 4,955,861, endeavors to provide a telephone exchange enabling a subscriber to notify the exchange of a telephone extension at the subscriber's present location so that calls directed to the extension will be directed to the telephone at the subscriber's present location. More contemporary practice in the art is represented by two patents to Otsuka, U.S. Pat. Nos. 5,392,340 and 5,469,501, entitled Telephone Exchange Apparatus and Communication Exchange Apparatus With Switching Of Communication Terminal Information, both disclose an arrangement for a telephone exchange in which the attributes of a subscriber may be changed from one extension number to another.
Other efforts in the art are represented by U.S. Pat. No. 5,392,346 issued to Hassler, et al., and entitled Mobile Log-In Capability Featuring Fixed Physical (Terminal-Dependent) Translations And Portable Logical (User-Dependent) Translations; U.S. Pat. No. 5,251,248 issued to Tokunaga, et al., and entitled Telephone Network Having Personal Number For Position-Independent; and U.S. Pat. No. 4,755,985 issued to Jayapalan, et al., and entitled Method And Apparatus For Facilitating Moves And Changes In A Communication System. I have found that contemporary practice in the art fail to effectively assure a shift of information for a subscriber in order to maintain the subscriber's previously used telephone number and grade when the site of installation of the subscriber's telephone is changed.